(CNN)Former New Jersey Gov. Chris Christie said Donald Trump's lies about the 2020 election results were a "red line" for him, and that he has not spoken with the former President in nearly a year.

       "The red line was Election Night, David," Christie, a Republican and former Trump ally, told David Axelrod on CNN's "The Axe Files" podcast released on Monday. "Standing behind the seal of the president and saying the election was stolen, and then offering not one piece of evidence to support that."

       Christie said that he spoke with one of Trump's sons that night and pressed them for evidence, recalling that he said, "If you have evidence that the election was stolen that's convincing, I'll fight with you." He did not mention the name of the son he spoke to but writes in his new book, "Republican Rescue: Saving the Party from Truth Deniers, Conspiracy Theorists, and the Dangerous Policies of Joe Biden," that he told Eric Trump in a text Election Night to lay out evidence of election fraud. Christie also told Axelrod he pressed Trump multiple times after the election for evidence of fraud.

       "I'm a prosecutor. Where's the evidence? He'd say these things that weren't evidence," Christie recalled to Axelrod. "So that's a red line for me, David. Like, I don't -- you can't undercut our democracy with no facts and that's why we haven't spoken since a couple of days before Christmas last year."

       Christie, who served as an adviser to Trump and helped him prepare for the presidential debates ahead of the 2020 election, has been outspoken against his claims that last year's election was stolen. He also blamed Trump's lies about the election results for the January 6 insurrection at the US Capitol, telling CNN's Dana Bash that it "incited people to that level of anger."

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       Asked about Trump's endorsement of Arizona Rep. Paul Gosar, a Republican who was censured by the US House and stripped of his committee assignments last week, Christie also told Axelrod the former President is engaged in "vendetta politics" that is bad for the GOP and the country.

       "It's bad for him, and he shouldn't be doing it. As his friend, I would tell him he shouldn't be doing it," he said. "Because whatever legacy he has as president, Operation Warp Speed, the economic performance, the conservative judges, the things that we, as Republicans would say, were good things. Every time he does stuff like this, it diminishes that, in my view."

       CNN's Rachel Jafanza contributed to this report.